APX Extended Fig-Forth: Writing a Full Screen Editor

As part of my work, I am hammering away on tools that I will need to write the game. One of the tools I absolutely want, is a full screen text editor, it will have very simple requirements:

split a 64 character fig-FORTH screen line into two 32 character windows, which when the cursor moves, will be scrolled over.

provide a way to switch between the following modes, selectable by the yellow keys:

Edit mode - Edit a given screen (OPTION)

Select Mode - Select a given screen (SELECT)

FORTH Mode - quickly type FORTH words to test things. (START)

The screen will be divided into a few areas, from top to bottom:

The Current Screen #

The Editing Window showing the current screen.

A Status Line (need to add this into my display list) showing EDIT MODE, SELECT MODE, or FORTH MODE.

A four line window for entering FORTH commands or showing edit HELP.

I have implemented initial versions of the needed words to setup the screen memory, to convert between ATASCII and ANTIC screen codes, various display primitives for writing to parts of the screen outside the E: device's reach (SEMIT, STYPE, SSPACE, SSPACES, SD.R, S.R, S., etc.). All of these words are written in FORTH, and I haven't sped anything up, so it does need some love there.

Now, I need to start writing the primitives to move around the displayed screen. I am posting a video here, enjoy